Mine are a mixture of rust, eroded rubber and chrome. I kind of lke the poor boy (that's me) image it evokes
I am probably showing my age but I say chrome, that said I have seen some body color bumpers that I like, mainly from the muscle car era, saw a killer 67 fairlane at the fall nationals yesterday I believe it was running super gas, beautiful airbrushed paint job but it had black wheels,grille bumpers, etc, no chrome at all, up close it was beautiful but from the grandstands it didn't look good, to me, the whole front of the car at a distance was just a black rectangle, on my crown and my pickup I like chrome, on my maverick,gto, I like body color bumpers, on my morris I think I would like grille to be body color with no bumpers at all!